1. Field of the Invention
The present invention relates to animal identification using iris images.
2. Background Art
In recent years animal identification has become a topic of intense worldwide interest in the aftermath of terrorist incidents, outbreaks of bovine spongiform encephalitis (BSE) and, more recently, reports of e. coli contamination in beef. Both food and performance animals are routinely assigned identifiers in the form of markings, ear tags, RFID chips, RFID boluses, etc. in order to prevent fraud and facilitate various business processes. The availability of reliable identification technology and a national animal registration program such as the USDA's National Animal Identification System (NAIS) will enable rapid traceability of animals and control of outbreaks of disease and contamination in the food supply.
Improved animal identification techniques are needed for a number of different animal species. In performance animals, such as horses, reliable identification is needed to prevent fraud in competitive events and sales transactions. In food animals such as cattle, swine, and sheep a national identification system has been developed by the US Department of Agriculture to facilitate traceability of diseased animals. In companion animals, such as cats and dogs, there is a need to identify lost and stray animals so they may reunited with their owners or, if an owner cannot be found, placed for adoption. Existing animal identification techniques such as ear tags, implantable radio frequency identification (RFID) devices, or ingestible RFID devices, are undesirable because they are expensive, invasive, and potentially harmful to the animal. In the case of performance animals such as horses, existing identification techniques such as sketches of unique markings and lip tattoos have limited accuracy and reliability. In the case of food animals such as cattle, ear tags can fall off and become lost and ingestible or implantable devices may not be successfully recovered and may end up in food products. Hence a more accurate, noninvasive means of animal identification is needed.
U.S. Pat. No. 4,641,349 discloses the use of the iris to derive unique identifiers for humans and animals, but does not describe specific techniques for dealing with the unique characteristics of animal irises. Similarly, U.S. Pat. No. 5,291,560 discloses a set of algorithms for segmentation of human iris images, generation of iris templates, and matching of templates to accomplish human recognition. But these techniques are not suitable for animals because most animals do not have circular pupils, the pupils do not have consistent shape, the pupils may not have regular boundaries, the limbus or outer boundary of the iris is in most cases not visible, and the iris texture patterns do not change consistently within the image as the pupil contracts or dilates. U.S. Pat. No. 6,424,727 discloses a system for animal identification based on circular iris features, but does not describe a method of iris recognition that is suitable for animals having non-circular iris features. U.S. Pat. Nos. 6,229,905 and 6,320,973 describe an animal identification method based on the shape of iridial granules that are present in the eyes of most horses and cattle that are at least 2 years old. But such granules are not present in most other animals thus the techniques described are not generally usable for species other than horses and cattle. U.S. Pat. No. 6,614,919 discloses iris recognition algorithms for horse eyes that use a precise pupil outline and approximation of the outer iris boundary to extract a portion of the iris area below the pupil, encode the iris texture using Gabor wavelets, form a digital code based on phase changes in the output of the wavelet encoding process, and match presented and reference codes using a distance metric. But this reference does not disclose any method for eliminating regions of the iris that are obscured by eyelids, incorporating the upper iris region or the unique features of the granula iridica, if present, in the digital iris code, or applying a variable-scale matching technique to accommodate the effects of changes in pupil size.